下面几种煤密度依次升高的是（）。
A.褐煤烟煤无烟煤
B.无烟煤烟煤褐煤
C.褐煤无烟煤烟煤
D.烟煤褐煤无烟煤
参考答案：A
绿色旅游饭店标准制定的基本原则有（）。
A.减量化原则
B.再使用原则
C.不可替代原则
D.再循环原则
The very ubiquity of electronic communications can have a surprising downside , notes Richard Kohn, a military historian at the University of North Carolina: a wife becomes accustomed to frequent e-mail from her husband, until he can’’t get to a computer. And then her anxiety increases.
A．failure
B．underside
C．drawback
D．consequence
